The coinfection of ALVs causes severe pathogenicity in Three-Yellow chickens.

The coinfection of ALVs (ALV-J plus ALV-A or/and ALV-B) has played an important role in the incidence of tumors recently found in China in local breeds of yellow chickens. The study aims to obtain a better knowledge of the function and relevance of ALV coinfection in the clinical disease of avian leukosis, as well as its unique effect on the pathogenicity in Three-yellow chickens. One-day-old Three-yellow chicks (one day old) were infected with ALV-A, ALV-B, and ALV-J mono-infections, as well as ALV-A + J, ALV-B + J, and ALV-A + B + J coinfections, via intraperitoneal injection, and the chicks were then grown in isolators until they were 15 weeks old. The parameters, including the suppression of body weight gain, immune organ weight, viremia, histopathological changes and tumor incidence, were observed and compared with those of the uninfected control birds. The results demonstrated that coinfection with ALVs could induce more serious suppression of body weight gain (P < 0.05), damage to immune organs (P < 0.05) and higher tumor incidences than monoinfection, with triple infection producing the highest pathogenicity. The emergence of visible tumors and viremia occurred faster in the coinfected birds than in the monoinfected birds. These findings demonstrated that ALV coinfection resulted in considerably severe pathogenic and immunosuppressive consequences.

Current Epidemiology and Co-Infections of Avian Immunosuppressive and Neoplastic Diseases in Chicken Flocks in Central China.

The avian immunosuppressive and neoplastic diseases caused by Marek's disease virus (MDV), avian leucosis virus (ALV), and reticuloendotheliosis virus (REV) are seriously harmful to the global poultry industry. In recent years, particularly in 2020-2022, outbreaks of such diseases in chicken flocks frequently occurred in China. Herein, we collected live diseased birds from 30 poultry farms, out of 42 farms with tumour-bearing chicken flocks distributed in central China, to investigate the current epidemiology and co-infections of these viruses. The results showed that in individual diseased birds, the positive infection rates of MDV, ALV, and REV were 69.5% (203/292), 14.4% (42/292), and 4.7% (13/277), respectively, while for the flocks, the positive infection rates were 96.7% (29/30), 36.7% (11/30), and 20% (6/30), respectively. For chicken flocks, monoinfection of MDV, ALV, or REV was 53.3% (16/30), 3.3% (1/30), and 0% (0/30), respectively, but a total of 43.3% (13/30) co-infections was observed, which includes 23.3% (7/30) of MDV+ALV, 10.0% (3/30) of MDV+REV, and 10.0% (3/30) of MDV+ALV+REV co-infections. Interestingly, no ALV+REV co-infection or REV monoinfection was observed in the selected poultry farms. Our data indicate that the prevalence of virulent MDV strains, partially accompanied with ALV and/or REV co-infections, is the main reason for current outbreaks of avian neoplastic diseases in central China, providing an important reference for the future control of disease.

The Emergence, Diversification, and Transmission of Subgroup J Avian Leukosis Virus Reveals that the Live Chicken Trade Plays a Critical Role in the Adaption and Endemicity of Viruses to the Yellow-Chickens.

The geographical spread and inter-host transmission of the subgroup J avian leukosis virus (ALV-J) may be the most important issues for epidemiology. An integrated analysis, including phylogenetic trees, homology modeling, evolutionary dynamics, selection analysis and viral transmission, based on the gp85 gene sequences of the 665 worldwide ALV-J isolates during 1988-2020, was performed. A new Clade 3 has been emerging and was evolved from the dominating Clade 1.3 of the Chinese Yellow-chicken, and the loss of a α-helix or ß-sheet of the gp85 protein monomer was found by the homology modeling. The rapid evolution found in Clades 1.3 and 3 may be closely associated with the adaption and endemicity of viruses to the Yellow-chickens. The early U.S. strains from Clade 1.1 acted as an important source for the global spread of ALV-J and the earliest introduction into China was closely associated with the imported chicken breeders in the 1990s. The dominant outward migrations of Clades 1.1 and 1.2, respectively, from the Chinese northern White-chickens and layers to the Chinese southern Yellow-chickens, and the dominating migration of Clade 1.3 from the Chinese southern Yellow-chickens to other regions and hosts, indicated that the long-distance movement of these viruses between regions in China was associated with the live chicken trade. Furthermore, Yellow-chickens have been facing the risk of infections of the emerging Clades 2 and 3. Our findings provide new insights for the epidemiology and help to understand the critical factors involved in ALV-J dissemination. IMPORTANCE Although the general epidemiology of ALV-J is well studied, the ongoing evolutionary and transmission dynamics of the virus remain poorly investigated. The phylogenetic differences and relationship of the clades and subclades were characterized, and the epidemics and factors driving the geographical spread and inter-host transmission of different ALV-J clades were explored for the first time. The results indicated that the earliest ALV-J (Clade 1.1) from the United States, acted as the source for global spreads, and Clades 1.2, 1.3 and 3 were all subsequently evolved. Also the epidemiological investigation showed that the early imported breeders and the inter-region movements of live chickens facilitated the ALV-J dispersal throughout China and highlighted the needs to implement more effective containment measures.

Avian leukosis virus (ALV) is highly prevalent in fancy-chicken flocks in Saxony.

The current prevalence of avian leukosis virus (ALV) in fancy chickens in Germany is unknown. Therefore, 537 cloacal swabs from 50 purebred fancy-chicken flocks in Saxony were tested for the presence of the ALV p27 protein using a commercial antigen-capture ELISA. The detection rate was 28.7% at the individual-animal level and 56.0% at the flock level. Phylogenetic analysis of PCR products obtained from 22 different flocks revealed the highest similarity to ALV subtype K. When classifying breeds by their origin, ALV detection rates differed significantly. Evaluation of questionnaire data revealed no significant differences between ALV-positive and negative flocks regarding mortality.

Molecular characteristic and pathogenicity analysis of a novel multiple recombinant ALV-K strain.

Avian leukosis virus (ALV) can induce various tumors and cause serious production problems. ALVs isolated from chickens were divided into six subgroups (A-J). In 2012, a strain of a putative novel subgroup of ALVs was isolated from Chinese native chickens in Jiangsu Province and named as ALV-K. In this study, three ALV-K strains (JS14LH01, JS13LH14, and JS15SG01) were isolated from chickens with suspected ALV infection in Jiangsu Province. Their complete genomes were amplified, sequenced, and analyzed systematically. The results showed that JS14LH01 and JS13LH14 were ALV-K and ALV-E recombinant strains. Whereas JS15SG01 is an ALV-K, ALV-E, and ALV-J multiple recombinant strain containing the U3 region of ALV-J. The pathogenicity test of JS15SG01 revealed that, compared with previous ALV-K strains, the viremia and viral shedding level of JS15SG01-infected chickens were significantly increased, reaching 100 % and 59 %, respectively. More important, JS15SG01 induced significant proliferation of gliocytes in the cerebral cortex of infected chickens, accompanied by the neurotropic phenomenon. This is the first report about a multiple recombinant ALV-K strain that could invade and injure the brain tissue of chickens in China. Our findings enriched the epidemiologic data of ALV and helped to reveal the evolution of ALV strains prevalent in chicken fields.

Diversity of Avian leukosis virus subgroup J in local chickens, Jiangxi, China.

Avian leukosis caused by avian leukosis virus (ALV) is one of the most severe diseases endangering the poultry industry. When the eradication measures performed in commercial broilers and layers have achieved excellent results, ALV in some local chickens has gradually attracted attention. Since late 2018, following the re-outbreak of ALV-J in white feather broilers in China, AL-like symptoms also suddenly broke out in some local flocks, leading to great economic losses. In this study, a systematic epidemiological survey was carried out in eight local chicken flocks in Jiangxi Province, China, and 71 strains were finally isolated from 560 samples, with the env sequences of them being successfully sequenced. All of those new isolates belong to subgroup J but they have different molecular features and were very different from the strains that emerged in white feature broilers recently, with some strains being highly consistent with those previously isolated from commercial broilers, layers and other flocks or even isolated from USA and Russian, suggesting these local chickens have been acted as reservoirs to accumulate various ALV-J strains for a long time. More seriously, phylogenetic analysis shows that there were also many novel strains emerging and in a separate evolutionary branch, indicating several new mutated ALVs are being bred in local chickens. Besides, ALV-J strains isolated in this study can be further divided into ten groups, while there were more or fewer groups in different chickens, revealing that ALV may cross propagate in those flocks. The above analyses explain the complex background and future evolution trend of ALV-J in Chinese local chickens, providing theoretical support for the establishment of corresponding prevention and control measures.

Molecular characterization of avian leukosis virus subgroup J in Chinese local chickens between 2013 and 2018.

Avian leukosis virus subgroup J (ALV-J) was first isolated from broiler chickens in China in 1999; subsequently, it was rapidly introduced into layer chickens and Chinese local chickens. Recently, the incidence of ALV-J in broiler and layer chickens has significantly decreased. However, it has caused substantial damage to Chinese local chickens, resulting in immense challenges to their production performance and breeding safety. To systematically analyze the molecular characteristics and the epidemic trend of ALV-J in Chinese local chickens, 260 clinical samples were collected for the period of 2013-2018; 18 ALV-J local chicken isolates were identified by antigen-capture enzyme-linked immunosorbent assay and subgroup A-, B-, and J-specific multiplex PCR. The whole genomic sequences of 18 isolates were amplified with PCR and submitted to GenBank. Approximately, 55.5% (10/18) of the 18 isolates demonstrated a relatively high homology (92.3-95.4%) with 20 ALV-J early-isolated local strains (genome sequences obtained from GenBank) in gp85 genes clustering in a separated branch. The 3' untranslated region (3' UTR) of the 18 isolates showed a 195-210 and 16-28 base pair deletion in the redundant transmembrane region and in direct repeat 1, respectively; 55.5% (10/18) of the 18 isolates retained the 147 residue E element. The U3 gene of 61.1% (11/18) of the 18 isolates shared high identity (94.6-97.3%) with ALV-J early-isolated local strains. These results implied that the gp85 and U3 of ALV-J local chicken isolates have rapidly evolved and formed a unique local chicken branch. In addition, it was determined that the gene deletion in the 3'UTR region currently serves as a unique molecular characteristic of ALV-J in China. Hence, the obtained results built on the existing ALV-J molecular epidemiological data and further elucidated the genetic evolution trend of ALV-J in Chinese local chickens.

Co-infection with avian hepatitis E virus and avian leukosis virus subgroup J as the cause of an outbreak of hepatitis and liver hemorrhagic syndromes in a brown layer chicken flock in China.

Hens of a commercial Hy-line brown layer flock in China exhibited increased mortality and decreased egg production at 47 wk of age. From 47 to 57 wk, average weekly mortality increased from 0.11 to 3.0%, and egg production decreased from 10 to 30%, with a peak mortality rate (3.0%) observed at 54 wk of age. Necropsy of 11 birds demonstrated tissue damage that included hepatitis, liver hemorrhage, rupture, and/or enlarged livers. Microscopic liver lesions exhibited hepatocytic necrosis, lymphocytic periphlebitis, and myeloid leukosis. While no bacteria were recovered from liver and spleen samples, avian hepatitis E virus (HEV) RNA was detected in all 11 tested hens by nested reverse transcription-polymerase chain reaction. Of these, subgroup J avian leukosis virus (ALV-J) proviral DNA was detected in 5 hens by PCR. Alignments of partial ORF2 gene sequences obtained here demonstrated shared identity (76 to 97%) with corresponding sequences of other known avian HEV isolates. Env sequences of ALV-J isolates obtained here shared 50.1 to 55% identity with other ALV subgroups and 91.8 to 95.5% identity with other known ALV-J isolates. Phylogenetic tree analysis of selected sequences obtained here grouped an avian HEV sequence with genotype 3 HEV and assigned an ALV-J sequence to a branch separate from known ALV-J subgroups. Immunohistochemical results confirmed the presence of avian HEV and ALV-J in livers. Therefore, these results suggest that avian HEV and ALV-J co-infection caused the outbreak of hepatitis and liver hemorrhagic syndrome observed in the layer hen flock analyzed in this study.

Molecular characteristics of the re-emerged avian leukosis virus in China, 2018-2019.

Since early 2018, avian leukosis virus (ALV) has re-emerged throughout six provinces in Northeast and East of China and caused huge economic losses. In different farms, there are significant differences in clinical symptoms, including morbidity, mortality and location of tumours, on affected animals, which implies that the present strains may have different origins and molecular characteristics. In this study, a systematic epidemiological investigation was conducted in 21 farms in six provinces. Results showed that the virus strains present in this outbreak are highly consistent but carry different mutations. All the strains shared 97.0%-99.0% identity with each other and were highly similar to the GD14J2 strain isolated previously, while different insertion fragments can be found in the env gene of different strains, suggesting that the strains of ALV in this outbreak may have the same ancestors but have gone through different evolutionary trajectories. This study demonstrated that these viruses may point to multiple sources of infection, and all should be identified and taken seriously in the formulation of control plans.

Co-infection of vvMDV with multiple subgroups of avian leukosis viruses in indigenous chicken flocks in China.

BACKGROUND: In China, although the ALV eradication program and the MD vaccination strategy greatly reduce the disease burdens caused by the infection of ALV and MDV, the frequent emergence of novel ALV-K or vvMDV in the vaccinated chicken flock challenges the current control strategies for both diseases. RESULTS: In Guangdong Province, an indigenous chicken flock was infected with neoplastic disease. Hematoxylin-eosin staining of the tissues showed the typical characteristics of MDV and classical ALV infection. The PCR and sequencing data demonstrated that the identified MDV was clustered into a very virulent MDV strain endemic in domestic chickens in China. Moreover, subgroups ALV-A and ALV-K were efficiently recovered from two samples. The full genome sequence revealed that the ALV-K isolate was phylogenetically close to the ALV TW3593 isolate from Taiwan Province. CONCLUSIONS: A co-infection of vvMDV with multiple ALV subgroups emerged in a chicken flock with neoplastic disease in Guangdong Province. The co-infection with different subgroups of ALV with vvMDV in one chicken flock poses the risk for the emergence of novel ALVs and heavily burdens the control strategy for MDV.

The emergence of the infection of subgroup J avian leucosis virus escalated the tumour incidence in commercial Yellow chickens in Southern China in recent years.

A total of 81 clinical cases of suspected tumours were submitted to our laboratory from Yellow chicken farms in southern China during the years 2010 through 2017. The tumour-like tissue samples were closely examined for common oncogenic avian viruses in cell culture and further analysed using polymerase chain reaction (PCR). During 2010-2012, Marek's disease virus (MDV) mono-infection was found to be the dominant cause of the tumour incidences (52.4%, 11/21) followed by co-infection of MDV+ALVs (19.1%, 4/21). Starting from the year 2013 the mono-infection of avian leucosis virus subgroup J (ALV-J) became the dominant agent of the tumour cases (83.3%, 5/6). During the most recent four years (2014-2017), co-infections involving ALV-J and MDV or between ALV subgroups have increased (23.4% and 18.5%, respectively), but each of the co-infections was still slightly lower than the ALV-J mono-infection incidence (33.3%). In contrast to the dominant MDV mono-infection cases before 2013, more recently, the emerging ALV-J mono-infection and ALV-J co-infections were largely responsible for the occurrence of avian virus-induced tumour incidences in the commercial local Yellow breeds of chickens in southern China. These results indicate that eradication measures against ALV on all chicken farms, especially on farms with the Yellow chickens, ought to be enhanced to reverse this trend.

Outbreak of myelocytomatosis caused by mutational avian leukosis virus subgroup J in China, 2018.

Avian leukosis virus subgroup J (ALV-J) was isolated in meat-type breeder chickens for the first time in 1988 in the United Kingdom. Due to the application of an eradication program, there were fewer reports related to myelocytomatosis or ALV-J in China after 2013. However, there was another breakout almost simultaneously in six provinces of China in February 2018. On-site, 15- to 20-week-old broiler breeder chickens showed depression, paralysis and weight loss. Mortality for certain flocks reached 15%. Sick chickens showed numerous yellow-white neoplasms growing in the sternum, rib and lumbar vertebra and had hepatic and renal metastasis. Histopathological observation showed all neoplasms were myelocytomas, and there were massive myelocyte-like tumour cells in the liver, kidney and bone marrow. To explore the aetiology of this re-outbreak of myelocytomatosis in China, we collected tumour-bearing chickens and isolated six strains of ALV-J (GM0209-1 to -6). Phylogenetic analysis of gp85 and gp37 showed GM0209 strains were clearly distinct from the prototype strain of ADOL-7501, HPRS-103 and NX0101, and there was a mutation, R176G, in the conserved region between hr1 and hr2 regions of gp85, which was not found in other 44 ALV-J strains. The 3'UTR nucleotide sequences of GM0209 isolates showed there was a signature deletion of 11 nt that was also present in 3'UTR sequences of SCDY1 and NHH, two isolates that have a reported association with haemangioma, indicating this deletion could not determine the tumour type induced by ALV-J. Although the eradication program of ALV-J has been successfully applied in China, the outbreak of ALV-J still occurred, and the virus strain spread quickly. Thus, the biocharacteristics and pathogenesis of mutational ALV-J should be further studied.

Molecular characteristics of avian leukosis viruses isolated from indigenous chicken breeds in China.

To assess the status of avian leukosis virus (ALV) infection in indigenous chicken breeds in China, 121 plasma samples collected from various indigenous chicken breeds were tested for the presence of ALV from 2015 to 2016. A total of 14 ALV strains were isolated and identified, including two ALV-A strains, one ALV-B strain, eight ALV-J strains, and three ALV-K strains. To study the genome structure, biological characteristics, and the evolutionary relationships of the ALV-K strains with other known subgroup strains from infected chickens, we determined the complete genome sequence of the three ALV-K strains and performed comparative analysis using the whole genome sequence or selected sequence elements. The replication rates of the three ALV-K strains were markedly lower than the rates of other ALVs, and they shared a common mutation in the pol gene, which had not been previously observed. In addition, nine putative recombinant events were detected in the genomes of the three newly isolated ALV-K strains, with high statistical support. This was the first report of an ALV-K reorganization event, which has contributed to its genetic evolution. In summary, we established a robust classification system for ALV, especially for ALV-K, and revealed additional genomic diversity for the ALV strains in indigenous chicken breeds. Therefore additional works are warranted to explore ALV genomics and epidemiology.

Co-infection of fowl adenovirus with different immunosuppressive viruses in a chicken flock.

In poultry, fowl adenovirus (FAdV) and immunosuppressive virus co-infection is likely to cause decreased egg production, inclusion body hepatitis, and pericardial effusion syndrome. In this study, fowl adenovirus infection was found in parental and descendent generations of chickens. We used quantitative polymerase chain reaction (PCR) and dot blot hybridization to detect the infection of reticuloendotheliosis (REV), avian leukosis virus (ALV), and chicken infectious anemia virus (CIAV) in 480 plasma samples. The test samples were 34.58% FADV-positive, 22.29% REV-positive, 7.5% CAV-positive, and 0.63% ALV-positive. Sequence analysis showed that FADV belonged to serotype 7, which can cause inclusion body hepatitis. The ALV strain was ALV-A, in which the homology of gp85 gene and SDAU09C1 was 97.3%. The positive rate was lower because of the purification of avian leukemia, whereas the phylogenetic tree analysis of REV showed that the highest homology was with IBD-C1605, which was derived from a vaccine isolate. Through pathogen detection in poultry we present, to our knowledge, the first discovery of fowl adenovirus type 7 infection in parental chickens and found that there was co-infection of FAdV and several immunosuppressive viruses, such as the purified ALV and CIAV. This indicates that multiple infection of different viruses is ever-present, and more attention should be given in the diagnosis process.

Characterizing the histopathology of natural co-infection with Marek's disease virus and subgroup J avian leucosis virus in egg-laying hens.

Marek's disease virus (MDV) and avian leucosis virus (ALV) are known to cause tumours in egg-laying hens. Here, we investigated the aetiology of tumours in a flock of egg-laying hens vaccinated against MDV. We carried out gross pathology and histopathological examinations of the diseased tissues, identified virus antigen and sequenced viral oncogenes to elucidate the cause of death in 21-22-week-old hens. At necropsy, diseased hens had distinctly swollen livers, spleens, and proventriculus, and white tumour nodules in the liver. The spleen and liver had been infiltrated by lymphoid tumour cells, while the proventriculus had been infiltrated by both lymphoid tumour cells and myeloblastic cells. Subtype J ALV (ALV-J) and MDV were widely distributed in the proventricular gland cells, and the lymphoid tumour cells in the liver and the spleen. In addition, positive ALV-J signals were also observed in parts of the reticular cells in the spleen. MDV and ALV-J antigens were observed in the same foci of the proventricular gland cells; however, the two antigens were not observed in the same foci from the spleen and liver. The amino acid sequence of the AN-1 (the representative liver tumour tissue that was positive for both ALV-J and MDV) Meq protein was highly similar to the very virulent MDV QD2014 from China. Compared to the ALV-J HPRS-103 reference strain, 10 amino acids (224-CTTEWNYYAY-233) were deleted from the gp85 protein of AN-1. We concluded that concurrent infection with MDV and ALV-J contributed to the tumorigenicity observed in the flock.

Seroprevalence of avian hepatitis E virus and avian leucosis virus subgroup J in chicken flocks with hepatitis syndrome, China.

BACKGROUND: From 2014 to 2015 in China, many broiler breeder and layer hen flocks exhibited a decrease in egg production and some chickens developed hepatitis syndrome including hepatomegaly, hepatic necrosis and hemorrhage. Avian hepatitis E virus (HEV) and avian leucosis virus subgroup J (ALV-J) both cause decreasing in egg production, hepatomegaly and hepatic hemorrhage in broiler breeder and layer hens. In the study, the seroprevalence of avian HEV and ALV-J in these flocks emerging the disease from Shandong and Shaanxi provinces were investigated. RESULTS: A total of 1995 serum samples were collected from 14 flocks with hepatitis syndrome in Shandong and Shaanxi provinces, China. Antibodies against avian HEV and ALV-J in these serum samples were detected using iELISAs. The seroprevalence of anti-avian HEV antibodies (35.09%) was significantly higher than that of anti-ALV-J antibodies (2.16%) (p = 0.00). Moreover, the 43 serum samples positive for anti-ALV-J antibodies were all also positive for anti-avian HEV antibodies. In a comparison of both provinces, Shandong chickens exhibited a significantly higher seroprevalence of anti-avian HEV antibodies (42.16%) than Shaanxi chickens (26%) (p = 0.00). In addition, the detection of avian HEV RNA and ALV-J cDNA in the liver samples from the flocks of two provinces also showed the same results of the seroprevalence. CONCLUSIONS: In the present study, the results showed that avian HEV infection is widely prevalent and ALV-J infection is endemic in the flocks with hepatitis syndrome from Shandong and Shaanxi provinces of China. These results suggested that avian HEV infection may be the major cause of increased egg drop and hepatitis syndrome observed during the last 2 years in China. These results should be useful to guide development of prevention and control measures to control the diseases within chicken flocks in China.

Molecular epidemiology of J-subgroup avian leukosis virus isolated from meat-type chickens in southern China between 2013 and 2014.

Members of avian leukosis virus subgroup J (ALV-J) cause various diseases associated with tumor formation and decreased fertility, resulting in major economic losses in the poultry industry worldwide. To assess the status of ALV-J infection in meat-type chickens in southern China, the molecular epidemiology of ALV-J strains was investigated. A total of 265 clinical samples collected from southern China from 2013 to 2014 were investigated in this study for the presence of ALV-J, which resulted in 12 virus isolates. Phylogenetic analysis showed that 91.7 % (11/12) of the ALV-J isolates have possessed high homology to Chinese layer isolates and belong to one subgroup. One of the ALV isolates (designated GD1411-1) was relatively closely related to the ALV-J broiler isolates, indicating that the GD1411-1 isolate might be a transition strain. Several unique nucleotide substitutions in gp85 and the U3 region were detected in all 12 ALV-J isolates. This study provides some interesting information on the molecular characterization of ALV-J isolates. These findings will be beneficial for understanding of the pathogenic mechanism of ALV-J infection.

Diagnosis and sequence analysis of avian leukosis virus subgroup J isolated from Chinese Partridge Shank chickens.

The diagnosis of avian leukosis virus subgroup J (ALV-J) infection in Chinese Partridge Shank chickens was confirmed by necropsy, histopathological examinations, antibody tests, viral isolation, immunofluorescence assays, and sequence analysis. Myelocytoma, myeloma, and fibrosarcoma were simultaneously found in Partridge Shank flock with ALV-J infection. Sequence analysis of the env genes of ALV-J demonstrated that both gp85 and gp37 were highly homologous among the three strains from local chickens of those among ALV-J strains isolated from white meat-type chickens. The phylogenetic trees indicated that the three strains isolated in this study were closely related to reference strains isolated in so-called Chinese yellow chickens and some strains isolated from white meat-type chickens, both from the USA and China. The observed ALV-J infection was the first report on Partridge Shank chickens, and myelocytoma, myeloma, and fibrosarcoma were found at the same time in this batch of local chickens.

First finding of subgroup-E avian leukosis virus from wild ducks in China.

To analyze the status of avian leukosis virus subgroup E (ALV-E) in wild ducks in China, we collected 276 wild ducks, including 12 species, from four provinces of China. The PCR detection for ALV-E identified four samples as positive samples and the detection rate was 1.45%. The env sequences of ALV-E were cloned and sequenced. In gp85, genes of the four ALV-E strains showed a high homology (98.1-99.5%) with ev-1, ev-3, and SD0501 and more than 90% homology with other subgroup-A and subgroup-B avian leukosis viruses. However, they showed a slightly lower identity with subgroup-J (NX0101 and HPRS103), from 47.5 to 48.1%. Simultaneously, a further comparison with ALV-E representative isolates indicated that the amino acid substitutions of the four wild duck strains were distributed throughout the gp85. In total, these results suggested that the subgroup-E avian leukosis virus has been found in wild ducks in China.

Genetic diversity and phylogenetic analysis of glycoprotein gp85 of avian leukosis virus subgroup J wild-bird isolates from Northeast China.

Avian leukosis virus subgroup J (ALV-J), first isolated in 1989, preferentially infects meat-type birds. Chinese layer flocks have experienced outbreaks of this virus since 2008. To analyze the status of ALV-J infection in wild birds in China, 585 wild birds collected from three provinces of Northeast China from 2010 to 2012 were tested, and six ALV-J strains were isolated for the first time. Furthermore, the gp85 genes of the six strains were amplified, cloned, and sequenced. The results indicated that two different ALV-J strains coexisted in Chinese wild birds from 2010 to 2012. These results not only expand the epidemiological data available for ALV-J and provide necessary information for the further understanding of the evolution of ALV-J, but they also highlight the potential role of wild-bird migration in the spread of ALV-J.